1. Field of the Invention
This invention relates to joint prostheses, particularly to finger knuckle joint prostheses.
2. Description of the Prior Art
U.S. Pat. No. 4,367,562 discloses an implantable joint prosthesis, to restore a finger joint or toe joint and consisting of a one-piece body of a material which is flexible and elastic and has tapering intramedullary stems extending in opposite directions from a central portion. The central portion is formed at an intermediate location with a relatively thin region defining the articulation axis and includes a pair of bulges which project in all directions transverse to the axis of the body outwardly of the respective stems on either side of this region and between the articulation region and the respective stem. The rounded bulge at the proximal side of the prosthesis is larger in volume than the rounded bulge at the distal side.
U.S. Pat. No. 3,745,590 discloses a prosthesis for use at joints, in particular those which require unrestricted orbiting motion such as the base of the thumb, carpal bones of the wrist and shoulder joints. The prosthesis comprises a molded body portion which replaces at least the articulating portion of the bone to be treated, and one or more ligamentous elements. The body portion is made of a biocompatible elastomer, especially one which is reinforced with a fibrous material such as a web or mesh of Dacron or Teflon. The ligamentous element can be a cord, a flat tape or a tube such as a fabric tube of Dacron or Teflon, and in some embodiments is protected against tissue ingrowth over at least its intermediate length. In a carpal-metacarpal prosthesis for a thumb, for example, the body portion also has a metacarpal stem portion having a tissue-ingrowth-receiving surface, such as a complete or partial covering of Dacron velour, the core of such stem being a biocompatible elastomer. The ligamentous element is tied or otherwise attached to a body tissue, for example to a bone or a tendon, in order to hold the articulating end of the body portion in its natural position. In an example in which the prosthesis is a carpal-metacarpal thumb prosthesis, the body portion is inserted in the metacarpal bone, the trapezium is excised and two ligamentous elements are brought to the flexor carpi radialis where their outer ends are inserted through an incision in the distal end zone of that tendon and tied thereto with slight slackness.